Environment and Air Traffic Noise
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ISEP 2006 ENVIRONMENT AND AIR TRAFFIC NOISE IGOR ŠTIMAC, B.Eng. E-mail:[email protected] Zračna luka Zagreb Pleso bb, 10000 Zagreb, Hrvatska JURICA IVANIŠEVIĆ, B.Eng. E-mail:[email protected] Zračna luka Zagreb Pleso bb, 10000 Zagreb, Hrvatska mr.sc ZLATKO SVIBEN,. E-mail: [email protected] Poštanska i telekomunikacijska škola Trg J. F. Kennedya 9, 10000 Zagreb, Hrvatska pollution of soil and water at airports. At its 50th Assembly, ABSTRACT IATA brought a Resolution on environment which fully supported the ICAO initiative about the revision of the The increase in the number of flights makes air traffic a restrictions in issuing the certificates which confirm that the serious problem of the present. Modern, jet aircraft generate deafening noise in the approach and takeoff of aircraft. Noise is airlines satisfy the criteria of noise, harmful exhaust emissions generated by aircraft engines letting out at high speed vortex and chemicals, all with the aim of reducing the negative impact exhaust gases, and in case of supersonic aircraft there is additional of air traffic on the environment. Adverse impact of thunder due to impact waves that follow takeoff or landing of anthropogenic polluters, including aircraft, affects to a great aircraft. In order to solve the problem of aircraft noise, some extent the global ecological balance in three main indications: alternative solutions will have to be implemented, such as - change in the balance of earth radiation due to replacement of the current air fleet by a new generation of aircraft anthropogenic greenhouse effect, related to the change or some immediate solutions such as the installation of hush-kits of global climate; and some special parts in the aircraft, which also affects the - change in the ozone in the atmosphere that affects the reduction of aircraft noise. Fast development of airports, resulting in problems related to noise, require finding of ways in which to intensity of radiation on the earth surface; harmonize development, modernisation of air traffic and the - change in the oxidation capacity of atmosphere due to “potential noisy adversaries” that occur as a consequence of the increase in the tropospheric concentration of ozone. technological development of airports. It is interesting to know the Regarding protection, today’s technology can respond to many values that define the noise as well as the values within which they requirements which first of all means the improvement of range, according to the valid regulations. In this way other traffic aircraft structure assemblies. The first aspect is the noise participants can understand the environment and take the attitude generated by aircraft, and the second aspect represents harmful of an active participant – define themselves to the measure of the emissions. The level of noise and the harmful exhaust emissions human. are regulated by the international (ICAO) and national regulations. The problems related to aircraft noise appeared Key words: noise, ecology, aircraft, airport when the number of operations during one day at one airport increased to such an extent that lives of the population living in 1. INTRODUCTION - CURRENT CONDITION the vicinity became intolerable. The introduction of jet aircraft resulted in protests of the population living around the airports Traffic degrades and devastates the environment and due to noise. It was impossible to live, especially below the every project of traffic development either on land, in the air, or approach and takeoff paths. Noise is generated by aircraft on water, needs to evaluate the volume of negative impact on engines which produce fast vortex exhaust gases. In case of the environment. The first knowledge about the harmful impact supersonic aircraft there is also additional thunder due to impact of traffic on the environment dates back to the sixties of the 20th waves which follow the takeoff or landing. When speaking of century. Today, life would be unthinkable without the transport noise generated by aircraft we think of the subjective feeling means, and yet their increase undoubtedly leads to the that an observer on ground feels due to the aircraft-generated destruction of the natural flora and fauna. An important noise. For noise measuring, a large number of measuring units milestone in the development of air traffic is the introduction of was defined and the most common is the decibel (dB). the jet propulsion in the sixties. The main ecological criteria Under the pressure of the public and the authorities, the airports related to international commercial aviation include aircraft have introduced additional measures to reduce the negative noise, aircraft engine emission, handling of waste material and impact of noise on the environment: by restricting the ISEP 2006 operations of noisy aircraft, by introducing certain procedures 1. the sum of EPNdBs for which the stipulated limits in approach and takeoff in order to reduce noise, by introducing were exceeded, does not exceed the value of 4 EPNdB approach-takeoff paths above less populated or unpopulated (for Chapter 2) i.e. 3 EPNdB (for Chapter 3 aircraft), areas, by banning night air traffic at airports, by sound- 2. value of EPNdB, for which the noise is greater at any insulation of houses i.e. buildings, by zoning of space, by point, does not exceed 3 EPNdBs (for Chapter 2) i.e. 2 moving. EPNdBs (for Chapter 3 aircraft), 3. the higher realized noise at one or two points is compensated by such reduction of noise in another or other points. 2. SOURCE OF AIRCRAFT NOISE The basic source of aircraft noise is the power plant. Propeller aircraft generate significantly lower noise compared to others. Noise generated by an operating turbo jet power plant occurs in all the basic engine elements. Noise generated by fans and compression spreads partially forwards and exits through Figure 1: Contours of noise of 100 EPNdB in approach and the suction nozzle, and partly spreads backwards and leaves the takeoff for a flight range of up to 1500 km engine through the fan nozzle. Noise generated in the combustion chamber exits through the central engine nozzle. In order to standardize the measurement of noise intensity in Also the mixing of the ambient air with the jet of exhaust gases certifying aircraft, ICAO stipulated standard conditions and produces certain noise since they flow at very high speed. Fan reference points in the vicinity of runways, determining the in flight generates also additional source of noise, and this is level of noise in landing or takeoff. These points are: noise that due to the interaction of fan blades and stator as well 1. Takeoff point (point A) – point on the runway axis and as the influence of their mutual location, wide range noise, that 6500 meters from the runway threshold. At this point is generated under the influence of the conversion of work from the noise intensity in the takeoff phase is measured, the fan blades on the air flow with the aim of obtaining maximal 2. Approach (point B) – point located on runway axis and effect of compression on a minimal space and whirring noise 2000 meters from the runway threshold. At this point which results from supersonic speed of airflow at the fan blade the noise intensity in landing phase is measured. tips. 3. Lateral point (point C) – point at lateral distance of The noise reduction can be influenced by using the material 650 meters from the runway. In this point the intensity which absorbs sound into the engine flow channel, by mixing of noise in the takeoff phase is also measured. outside cold and interior warm flow of air or by installing hush- kits at the exit of the central nozzle. The first reduction of noise occurred with the appearance of omni-flow turbo-jet power plants with low level of two-flow, and later with the occurrence of power plants with high level of two-flow. Another element which causes noise is the planner. Noise generated by planner results from pulsing of aerodynamic forces on the wing, by the existence of turbulent boundary layer and vortex which occurs in air flowing around the surfaces of Figure 2: Noise measurement points wings, fuselage and tail planes, as well as the airflow around landing gears, flaps and various other protrusions on the Every point at which the level of noise is measured has its fuselage. During takeoff the level of noise caused by the limit values compared to the aircraft weight. These values have planner is irrelevant, whereas noise generated in approach or to be complied with. Every country determines for itself its limit landing is of great importance and regarding intensity can be value. The new noise measurement unit is called EPN dB compared to the noise of power plants. According to ICAO (Effective Perceived Noise decibel). Since there are no precise standards ANNEX 16 Chapter 2, the noise level of planner is mathematical methods to determine the noise level for the stipulated at 8-10 EPNdB lower than the level of total noise, mentioned three points, during the design of aircraft the final and in Chapter 3 the level has been stipulated at 5-7 EPNdB of values of noise level are determined experimentally by the total noise intensity. recording the aircraft. During recording it may happen that the aircraft exceeds the limit noise level stipulated by the regulation at one or two points. Such aircraft may get the certificate for the satisfaction of noise level if: ISEP 2006 3. METHODS OF AIRCRAFT NOISE REDUCTION approach. The standard procedure represents aircraft landing from the altitude of 1500 – 2000 ft above the airport of landing. There are two approaches in the global solving of the In this flight the pilot receives first the signal of the marker ecological problem of noise.